ON MOUNTING. 151 



process," which was invented by the author in 1870, 

 and the success of which induced him to devise the 

 necessary modifications upon it and to construct the 

 necessary appliances in order to adapt it to the 

 mounting of histological and other preparations. 

 Slides of " selected " diatoms should be mounted in 

 the same manner, the forms being picked up by 

 means of a carefully chosen hair from the dried hide 

 of a cow the soft and flexible hairs taken from 

 the under side of the neck being those most suitable 

 for the purpose. These hairs are to be affixed to 

 the cedar sticks used with " camel-hair pencils " by 

 means of sealing-wax dissolved in alcohol, and a 

 number should be prepared, having the hairs of 

 different lengths in order to obtain varieties of 

 strength and elasticity. Some hairs should be 

 mounted of considerable length, as the mounter of 

 diatoms and other such minute specimens must 

 learn to put them back symmetrically into their 

 required positions under the microscope, and in, the 

 balsam when they float away ; a little practice will 

 soon lead to the acquirement of this absolutely 

 necessary skill, and it will be found not difficult to 

 heat the hardened balsam (many times if necessary), 



lines faintly from each top corner to its opposite bottom corner ; 

 the intersection of these lines will give the exact centre of the 

 slip, which can be marked by a dark spot. 



Thirdly. "With a writing-diamond make, upon a slip, placed 

 on a turn-table, concentric circles, gin., fin., fin., and -pn. 

 in diameter ; each sized cover can then be placed precisely 

 in the centre, if the slip on which the cover is to be placed 

 is laid upon that upon which the circles have been described, 

 the circles, of course, being clearly visible through the super- 

 imposed slip. 



